1. Field of the Invention
The present invention relates to a photosensitive resin, a photosensitive composition, and a photo-crosslinked structure obtained from the composition. More particularly, the invention relates to a photo-crosslinked structure which has a higher-order structure and which allows an arbitrary site of a substrate surface to be hydrophilic.
2. Description of Related Art
Conventionally, a variety of photosensitive resins having a hydrophilic polymer serving as a backbone and photosensitive compositions containing such a photosensitive resin have been proposed. Among them, an example of such resins which have ever been developed is a photosensitive resin having a saponified polyvinyl acetate moiety in a backbone (see Patent Document 1). Although the saponified polyvinyl acetate is water-soluble and applicable to a substrate in the form of water-based aqueous solution, a photo-crosslinked structure thereof has such high water resistance that allows the structure to be produced through development with water. However, the photo-crosslinked structure produced from the photosensitive resin has a surface having a static contact angle—an index for hydrophilicity—as high as about 50°, which is unsatisfactory from the viewpoint of imparting hydrophilicity to a substrate surface.
Patent Document 1 also discloses photosensitive compounds; i.e., a polyoxypropylene-polyoxyethylene copolymer having an amino group at each end and a polyoxyethyleneamine (Jeffamine series, products of Huntsuman Corporation), with a photosensitive group having been introduced to each end of these polymers. However, photosensitive compounds produced from polyoxypropyleneamine-polyoxyethylene copolymer having an amino group at each end (Jeffamine ED-600) or polyoxyethyleneamine (Jeffamine EDR-148) have considerably poor solubility in water, and photo-crosslinked structures obtained from the compounds fail to attain sufficient film strength and to have a stable hydrophilic surface.
In order to control adsorption of a physiologically active substance or a similar substance on an interface between the substance and a structure such as a medical device, there has been proposed provision of a surface having excellent bioadaptability through formation of a hydrophilic surface by use of a photo-crosslinked structure obtained from a photosensitive composition containing a hydrophilic polymer having an azido group (see Patent Document 2). However, photosensitive compositions disclosed in Patent Document 2 produced from an acrylamide derivative or a similar substance serving as a hydrophilic polymer having an azido group fail to attain sufficient film strength and to have a stable hydrophilic surface.    [Patent Document 1] Japanese Patent Application Laid-Open (kokai) No. 2003-292477 (paragraphs including [0013] and [0046])    [Patent Document 2] Japanese Patent Application Laid-Open (kokai) No. 9-103481 (paragraphs including [0044])